大型电力变压器铁心剩磁退磁方法的研究

发布时间：2018-07-05 08:51

本文选题：电力变压器 + 铁心　；参考：《华北电力大学》2017年硕士论文

【摘要】：大型电力变压器铁心磁路内的剩磁问题是普遍存在的,随着电力系统的大力发展,电力变压器的容量越来越大,电压等级越来越高,大型电力变压器铁心内的剩磁问题也越来越严重,尤其是发电站的升压变压器、用于直流输电的换流变压器、变电站的主变,其铁心剩磁的问题表现的最为严重。剩磁问题具体表现为增大变压器的空载有功损耗;增大变压器铁心的震动;增大变压器噪音水平,形成噪音污染;当电力变压器铁心剩磁非常严重时,对变压器的现场空载合闸试验非常不利,造成变压器空载合闸励磁涌流过大,出现继电器保护动作跳闸现象;跳闸产生的操作冲击过电压会高于变压器的额定电压,这可能造成变压器的绝缘损伤;励磁涌流过大会使得铁心磁通高度饱和,铁心出现局部过热现象,对铁心造成损伤;温度过高会使绝缘老化加快,变压器油裂解,从而影响变压器的运行寿命,严重影响了电力系统的安全稳定运行。因此判断变压器铁心内是否有剩磁、如何消除铁心剩磁已成为人们日益关注的重点问题。通过分析大型电力变压器的工作原理、结构特点,发现大型变压器均为油浸式,其铁心磁路本身是封闭回路,并且铁心和绕组完全被变压器油箱密封屏蔽起来,因此采用常规的磁场测量方法不能实现对变压器铁心内的磁场测量。本文中采用的测量铁心磁场的方法是利用绕组本身作为测量线圈,根据铁心的励磁曲线的特性(饱和磁通和剩余磁通等特性),通过测量变压器绕组首尾两端电压,并对电压曲线进行积分计算来准确测量出铁心内的磁通变化量,准确计算出铁心的最大饱和磁通量、饱和剩磁量和铁心的初始剩余磁通量;并根据以上的铁心磁通测量方法研究出新型退磁的方法:利用直流电源对铁心施加与其剩余磁通量反方向的且等值的磁通量。通过对不同类型的电力变压器进行退磁,验证了利用此方法去除铁心剩磁是十分有效的。
[Abstract]:The problem of remanence in the core magnetic circuit of large power transformer is widespread. With the development of power system, the capacity of power transformer becomes larger and larger, and the voltage grade becomes higher and higher. The problem of remanence in the core of large power transformer is more and more serious, especially in the booster transformer of power station, the converter transformer used for DC transmission, the main transformer of substation, the problem of core remanence is the most serious. The problem of remanent magnetism is to increase the no-load active power loss of the transformer; to increase the vibration of the transformer core; to increase the noise level of the transformer; to form noise pollution; when the remanence of the core of the power transformer is very serious, It is very unfavorable to the field no-load closing test of the transformer, which causes the inrush current of the transformer's no-load closing excitation to be too large, the phenomenon of relay protection action tripping occurs, and the operation impulse overvoltage produced by the tripping is higher than the rated voltage of the transformer. This may cause insulation damage to transformers; excessive excitation inrush current causes high saturation of magnetic flux in the core, local overheating of the iron core, and damage to the iron core; excessive temperature will speed up insulation aging and the transformer oil will break up. Therefore, the operation life of transformer is affected, and the safe and stable operation of power system is seriously affected. Therefore, how to determine whether there is remanence in the core of transformer and how to eliminate the remanence of the core has become an increasingly important issue that people pay more and more attention to. By analyzing the working principle and structural characteristics of large power transformers, it is found that the large transformers are oil-immersed, the core magnetic circuit itself is a closed loop, and the core and winding are completely sealed off by the oil tank of the transformer. Therefore, the conventional magnetic field measurement method can not be used to measure the magnetic field in the transformer core. In this paper, the method of measuring the core magnetic field is to use the winding itself as the measuring coil. According to the characteristics of the excitation curve of the core (saturation flux and remanent flux, etc.), the voltage between the two ends of the transformer winding is measured. The integral calculation of the voltage curve is carried out to accurately measure the flux variation in the core and calculate the maximum saturated magnetic flux, saturated remanent magnetic flux and initial residual flux of the core accurately. A new method of demagnetization is developed according to the above methods of core flux measurement: the DC power source is used to apply the equivalent magnetic flux in the opposite direction to the iron core in the direction of its remanent magnetic flux. Through demagnetization of different types of power transformers, it is proved that this method is very effective in removing core remanence.
【学位授予单位】：华北电力大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM41

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